An international research team has successfully propagated a commercial hybrid rice variety as a clone through seeds with 95 percent efficiency. According to the team, this could lower the cost of hybrid rice seeds and make high-yielding, disease resistant rice varieties available to low-income farmers worldwide.
Rice, the staple crop for half of the global population, is costly to breed as a hybrid for a yield improvement of about 10 percent. One of the solutions to this would be to propagate hybrids as clones that would remain identical from generation to generation without further breeding. Many wild plants can produce seeds that are clones of themselves, a process called apomixis. However, transferring apomixis to a major crop plant has proved difficult to achieve. In 2019, a team at the University of California Davis (UC Davis) led by Professor Venkatesan Sundaresan and Assistant Professor Imtiyaz Khanday achieved apomixis in rice plants, with about 30 percent of seeds being clones. Sundaresan, Khanday, and colleagues in France, Germany, and Ghana have now achieved a clonal efficiency of 95 percent, using a commercial hybrid rice variety. The team also showed that the process could be sustained for at least three generations.
The single-step process modifies three genes called MiMe, which cause the plant to switch from meiosis to mitosis. Another gene modification induces apomixis, and resulting in a seed that grows into a plant genetically identical to its parent. “Apomixis in crop plants has been the target of worldwide research for over 30 years, because it can make hybrid seed production accessible to everyone,” Sundaresan said. He also noted that the increase in yields can help meet the global needs of an increasing population without having to increase land, water, and fertilizer use.